My deck with which I reached rank 6 yesterday after reaching level 10 the day before has something like 32 or 33 cards (SK buff/debuff deck so no discard deck) with lots of multiples in there. Do I always get exactly the cards I want? Surely not, but on the other hand this deck allows me to adjust my strategy during mulligan phase for round 1 depending on what enemy deck I face and which cards I drew, since it allows for a few good strategies/strategy mixes that can counter a variety of enemy decks. If I face a NG deck, for example, I make sure to keep a lot of cards that can harm my own units, like Brokvar Hunter, my Light Longships, and of course Bloodcurling Roar, which sets me up for my "buff the longships" strategy. If I face a monster deck (especially with Dagon), I will keep more First Lights if I drew more than one, although I typically mulligan doubles of this card away facing most other decks. It's not perfect but it works for me for now and allows me a certain flexibility within a single deck.